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Re: achieving very low latency
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Re: achieving very low latency


  • Subject: Re: achieving very low latency
  • From: "Stephen F. Booth" <email@hidden>
  • Date: Wed, 04 Jul 2012 14:48:19 -0400

What does your code look like- are you using an AUGraph or just an output Audio Unit? When are you calling AudioOutputUnitStart or AUGraphStart? I seem to recall that AUGraphStart can take a bit of time, so in your case it might be better to have the graph/AU running but outputting silence and then enqueue your buffer as normal into that.

Stephen

On 7/4/12 2:28 PM, Daphne Ippolito wrote:
I've tried buffers of 32 bytes, and I still get ~30 ms of delay. I
don't think I can go much lower than that? I am using an only slightly
revised version of the sample code from the Learning Core Audio book.

-Daphne

On Wed, Jul 4, 2012 at 2:18 PM, Robert Martin<email@hidden>  wrote:
Use smaller buffers?

On Jul 4, 2012, at 11:42 AM, Daphne Ippolito wrote:

In the experiment, a physical pushbutton is pressed (the old system used a
National Instruments card to record this; I am using an Arduino) that plays
a sound. I am referring to latency as the time between when the physical
button is pressed and when the sound outputs from the audio jack. I have
been measuring this with an oscilloscope.

With Core Audio, I have not been able to get this time gap lower than 30
ms. I have tested the Arduino independently and it is not contributing more
than 1 ms of delay.

This is my first time programming with audio, so I am still a bit unclear
on how it works. I've been told that I can't have more than 10 ms delay
between when the pushbutton is pressed and when the sound leaves the
speakers, and preferably less than 1 ms.

Any advice on how I can accomplish this?
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References: 
 >achieving very low latency (From: Daphne Ippolito <email@hidden>)
 >Re: achieving very low latency (From: Paul Davis <email@hidden>)
 >Re: achieving very low latency (From: Daphne Ippolito <email@hidden>)
 >Re: achieving very low latency (From: Robert Martin <email@hidden>)
 >Re: achieving very low latency (From: Daphne Ippolito <email@hidden>)

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